A Vietnam-flagged tanker with 18 crew members on board has gone missing since leaving Singapore for a Vietnamese port last Thursday, raising fears that it has fallen into the hands of pirates.

The vessel was carrying more than 5,200 tons of oil products and was scheduled to arrive at its destination, Cua Viet, in central Quang Tri province on Sunday.

Vietnamese search and rescue authorities tell VOA’s Vietnamese service that they lost radio contact with Sunrise 689 less than an hour after its departure.

Nguyen Vu Diep, official from the Hai Phong Fisheries Shipbuilding Company, which owns the missing tanker, said it is very likely that it has been taken by pirates.

“It is a 90 percent possibility that the tanker was hijacked. If the pirates demand ransoms, it will be very tough for us as we are not economically strong at the moment. Hopefully they will take away all the products and release the ship and its crew," said Diep.

Vietnam, which did not tell the media about the missing tanker until Monday, has asked Singapore, Malaysia, Indonesia and the Philippines to help track down the ship.

Relatives of the sailors are gathering in the northern port of Hai Phong to await news of their loved ones.

Nguyen Thi Thu Lan, the wife of one of the crew members, said everyone is trying to remain positive and optimistic.

“I do not know what to do now. We really hope rescue authorities have some updates about the ship [soon]. Our greatest hope is that they will return home safely," said Lan.

According to the International Maritime Bureau's Piracy Reporting Center, Southeast Asia has seen at least six cases of coastal tankers being hijacked for their cargo since April of this year.

This report was produced in collaboration with the VOA Vietnamese service.